Dilatation balloon catheters are frequently used for the treatment of stenosis in the coronary arteries. This procedure is known as percutaneous transluminal coronary angioplasty (PTCA). According to this procedure, blockage in a coronary artery can be reduced by positioning a balloon dilatation catheter across the blockage and inflating the balloon, which causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery.
The procedure starts with the introduction of a guiding catheter into the cardiovascular system of a patient through the femoral artery in the groin area. The guide catheter is advanced through the arteries until its distal end is located near the desired coronary artery. Next a guidewire and balloon dilatation catheter are introduced into the guide catheter. The guidewire is first advanced out of the guiding catheter into the patient's coronary artery and is positioned across the stenosis. The dilatation catheter is then slid over the guidewire until the dilatation balloon is properly positioned across the stenosis. The balloon is then inflated to compress the stenosis and dilate the artery.
It is often desirable to do more than simply force a balloon against the stenosis or other restriction to compress any plaque in the artery wall and to open the lumen more fully. In many cases there may be restenosis of the artery, which may require another angioplasty procedure or a surgical bypass operation. To help prevent the artery from closing again, a physician can implant a stent inside the artery. A stent is a cylindrically shaped wire formed device intended to act as a permanent prosthesis. The stent is usually delivered to the artery in a compressed shape on a stent delivery catheter and expanded to a larger diameter once in place by a balloon.
In general, the typical procedure for implanting a stent includes first opening the artery with a balloon dilatation catheter procedure, as noted above. Once the artery is dilated, the balloon dilatation catheter is exchanged with another catheter carrying a stent. There are different methods used to exchange the balloon catheter with a stent delivery catheter. For an over-the-wire catheter, this involves exchanging the guidewire with an extension wire or extending the guidewire to allow catheter exchange. These methods can be difficult and time consuming.
Once the dilatation catheter is removed, the stent delivery catheter must be inserted. The stent delivery catheter is then advanced through the guide catheter to the stenosis and the stent is positioned to bridge the weakened portion of the artery. The balloon is then inflated and the stent is placed in the artery. Many patents disclose the construction and design of stents as well as the apparatus for positioning the stent in the artery. U.S. Pat. No. 4,733,665 to Palmaz discloses a number of stent configurations and a delivery catheter with the stent mounted on the inflatable portion of the catheter prior to insertion in the guide catheter. The stent is implanted by positioning it within the artery and monitoring its position on a viewing monitor. Once the stent is position as desired, the catheter is expanded and the stent is separated from the catheter body. The catheter is then withdrawn, leaving the stent in place in the artery. U.S. Pat. No. 4,886,062 to Wiktor, assigned to the same assignee as the present invention, discloses a stent carried on a dilatation balloon prior to insertion in the guide catheter and is positioned in the artery via a guiding catheter. The prior art does not allow loading the stent on the balloon of the dilatation catheter during the procedure without removing the catheter from the body or requiring a catheter exchange. This does not allow the physician the flexibility to use the same balloon catheter for dilatation and stent delivery or load the stent anytime during the procedure.
Guide catheters are known in the prior art. U.S. Pat. No. 4,516,972 to Samson shows a guiding catheter and method of manufacture having an inner liner made of slippery material, an intermediate layer of flexible material wound from ribbons to provide torsional rigidity and an outer jacket of flexible material all bonded together. U.S. Pat. No. 4,817,613 to Jaraczewski shows a guiding catheter and method of construction having a multiple layer construction with an inner flexible member surrounded by a pair of torque transmitting layers encased by an outer layer applied as a viscus material and cured to harden, joining the layers together.
Crimping stents on the end of dilatation balloons using a bladder technique is known in the prior art. European Patent Application Publication number 0630623A2 to Williams discloses a mechanism for stent loading on a catheter. The bladder described has an open end and a sealed end. A stent is loaded in the open end of the bladder, the collapsed balloon of a dilatation catheter is then inserted inside the stent. The bladder is then inflated to affix the stent to the balloon. The delivery catheter, now loaded with a stent, is ready to be inserted into the body of a patient for deployment. Williams device uses the bladder in a separate tool for loading stents onto balloon catheters prior to use.
Balloons and guide catheters are also known in the prior art. European Patent Application Publication number 0416734A1 to Coehlo, European Patent Application Publication number 0415332B1 to Keith, U.S. Pat. No. 5,395,389 to Patel, and U.S. Pat. No. 5,388,590 to Horrigan et al. have balloons with inflation lumens that are assembled in the guide catheter or are inserted into the guide catheter. When the balloons are inflated, the guidewire is trapped in place during a catheter exchange.